I’m not sure what you mean by the social media buttons only appearing on posts. They are displayed at the top of the page by default as in the demo here: http://www.kriesi.at/themes/coherence/

You can add more social media icons in the Theme Options. Just scroll down to where you see the current Social Icons and hit the Green + sign to add another. Then select Linkedin from the dropdown and put your URL into the field next to it. Make sure to Save all changes when you are done.